1. Field of the Invention
The present invention relates to a vehicle lamp, and more particularly to a vehicle headlight generally referred to as a projector-type headlight (Poly Ellipsoid Headlamp; PES) using an ellipse group reflecting surface (e.g., a spheroid reflecting surface), a projection lens with an aspheric surface, and a shutter for adjusting a light distribution characteristic. The light can be configured to switch between a meeting-beam (or low-bean) distribution and a running-beam (or high-beam) distribution.
2. Description of the Related Art
Referring now to FIG. 1, a conventional projector-type headlight 90 will be described. The projector-type headlight 90 comprises a light source 91, an ellipse group reflecting surface 92, a shutter 93, and a projection lens 94. The ellipse group reflecting surface 92 is a reflecting surface configured as a spheroid, a complex ellipse, or the like, having a first focus f1 and a second focus f2. The light source 91 is arranged at a position corresponding to the first focus f1, while the shutter 93 is arranged at a position in the vicinity of the second focus f2 of the ellipse group reflecting surface 92. The focus of the projection lens 94 is arranged in the vicinity of the shutter 93. In the projector-type headlight 90 thus constructed, the movement of the shutter 93 allows a desired low-beam distribution pattern and a desired high-beam distribution pattern in a selective manner.
More specifically, in a vehicle headlight constructed as described above, a light beam from the light source 91 is reflected by the ellipse group reflecting surface 92 and is then provided as reflection light having a generally circular cross section that converges at the second focus. A lower half of the reflection light is shaded when the shutter 93 is placed in the optical path of the reflection light. Thus, the resulting reflected light is shaped as a generally upper semicircular part. The generally upper semicircular part of the reflected light is projected in the irradiation direction and turned upside down by the projection lens 94 to become a lower semicircular part of the reflected light. In other words, as shown in FIG. 2, a light distribution pattern HS suited for low-beam distribution, which does not include high beam light rays, can be obtained.
On the other hand, the shutter 93 may be configured to be movable. If a high-beam distribution pattern is required, the shutter 93 can be withdrawn from the optical path of the light reflected from the reflecting surface 92. Thus, the lower semicircular part of the reflected light which can form a high bean and which is shaded by the shutter 93 in low-beam mode is allowed to be projected as irradiation light, resulting in a high-beam distribution pattern HM as shown in FIG. 3.
In the conventional projector-type headlight 90, however, the lower half of the reflected light from the ellipse group reflecting surface 92 is shaded at the time of low-beam distribution. As a result, the amount of light provided by the low-beam distribution can be poor in supply. To solve such a disadvantage, in general, an insufficient amount of light is compensated by, for example, inclining the optical axis of the headlight to the lower left side when it is intended for driving on the left-hand side (In Japan, automotive vehicles drive on the left side) such that the portion corresponding to the point P that has a high degree of brightness is not shaded by the shutter 93 (see FIG. 2).
On the other hand, if the shutter 93 is withdrawn from the above configuration of the headlight which provides adequate low-beam distribution, there is not enough irradiated light directed to the front (see FIG. 3). Therefore, there is another problem in that there is insufficient distance visibility for high-beam distribution.
In the projector-type headlight 90, generally, there is a further problem of poor visibility in both left and right directions because the width of irradiation light in these directions is not enough.
In order to solve the above and other problems of the conventional art, therefore, it is an object of the present invention to provide a projector-type vehicle headlight, by which a low-beam distribution and a high-beam distribution can be selectively employed, and unused light can be effectively used as reflection light in each of the low- and high-beam distributions. The projector-type headlight is especially capable of attaining a sufficient illumination in the high-beam distribution.
Furthermore, it is another object of the present invention to provide a headlight capable of improving visibility by applying a sufficient illumination in both left and right directions at the time of high-beam distribution.
In order to attain the objects of the invention, a vehicle headlight according to the present invention can be embodied in a device that includes a light source; a first ellipse group reflecting surface having an optical axis direction substantially corresponding to the irradiation direction of the headlight, the first ellipse group reflecting surface having a first focus and a second focus, the first focus being located substantially at the light source, the first ellipse group reflecting surface configured to reflect light irradiated from the light source in the irradiation direction of the headlight; a projection lens having a focus in the irradiation direction of the headlight and in the vicinity of the second focus of the first ellipse group reflecting surface, the projection lens configured to project light irradiated from the light source and light reflected from the first ellipse group reflecting surface in the irradiation direction; a second ellipse group reflecting surface having an optical axis crossing the optical axis of the first ellipse group reflecting surface, the second ellipse group reflecting surface having a primary focus and a secondary focus, the primary focus of the second ellipse group reflecting surface located substantially at the light source; a first parabolic group reflecting surface having a focus located substantially at the secondary focus of the second ellipse group reflecting surface, the first parabolic group reflecting surface configured to reflect light reflected from the second ellipse group reflecting surface in the irradiation direction of the headlight; a second parabolic group reflecting surface having an optical axis substantially corresponding to the irradiation direction of the headlight, the second parabolic group reflecting surface having a focus located in the vicinity of-the light source, the second parabolic group reflecting surface being arranged in the irradiation direction side from the first ellipse group reflecting surface; and a shutter provided in the vicinity of the focus of the projection lens, the shutter being capable of being placed in and withdrawn from an optical path of light reflected from the first ellipse group reflecting surface, the shutter having a shutter part and a shade part, the shutter part providing a low-beam light distribution pattern by being placed in the optical path of the reflected light from the first ellipse group reflecting surface and providing a high-beam light distribution pattern by being withdrawn from the optical path, the shade part shading light traveling from the light source to the second parabolic group reflecting surface when the shade is in a first position, and providing light from the light source to the second parabolic group reflecting surface when the shade is in a second position.
In the above configuration of the vehicle headlight, at first, when the headlight is in the low-beam distribution (which is normally used), unused light from the first ellipse group reflecting surface is captured on the second ellipse group reflecting surface, and the captured light is then projected from the first parabolic group reflecting surface toward the irradiation direction to allow the headlight to provide more illumination in the low-beam distribution. Therefore, there is an extremely superior effect in improvement of visibility in the low-beam distribution.
The high-beam distribution pattern can be constructed such that it is compensated with light being irradiated like a spot illumination in a direction towards the front of the vehicle by the second parabolic group reflecting surface. In the conventional art, on the other hand, such a high-beam distribution pattern is insufficient because it is inclined to the lower left side for increasing the visibility in the low-beam distribution. The headlight of the invention can also be configured such that the distribution of light from the first parabolic group reflecting surface is added to the high-beam distribution pattern. Consequently, an extremely superior effect in improvement of visibility at each of the low- and high-beam distributions can be attained. In addition to the above, sufficient illumination can be provided in the left and right directions.
In the embodiment of the vehicle headlight as described above, it is preferable to arrange the first ellipse group reflecting surface and the second ellipse group reflecting surface such that the second focus of the first ellipse group reflecting surface is on the outside of the second ellipse group reflecting surface. Also, it is preferable to locate the shutter part of the movable shutter on a back side of the second ellipse group reflecting surface when the shutter part is withdrawn from the optical path of the reflected light from the first ellipse group reflecting surface.
In one of the preferred embodiments, the movable shutter may be rotatably fixed on a substantially horizontal axis to be placed in or withdrawn from the optical path of the headlight.
It is preferred that the second parabolic group reflecting surface be composed of a pair of reflecting surfaces provided on left and right sides of the first ellipse group reflecting surface in the horizontal direction such that the second parabolic group, reflecting surface receives direct light from the light source when the movable shutter is withdrawn.
Preferably, the vehicle headlight according to the present invention includes shading means for shading the light reflected from the second ellipse group reflecting surface to the first parabolic group reflecting surface when a high-beam distribution is achieved. The shading means may be driven independently of the movable shutter. Alternatively, the shading means may be interlocked with the movable shutter. The shading means and the movable shutter may be rotated around a substantially horizontal axis.
In the embodiment of the vehicle headlight described above, the second ellipse group reflecting surface preferably has an opening portion coinciding with a part of a light path of irradiation light from the light source and reflected light from the first ellipse group reflecting surface to the projection lens. In this case, the movable shutter can shade a part of the opening portion when it is placed in the optical path, and open the opening portion when it is withdrawn from the optical path.
Further, in the vehicle headlight with the afore-mentioned constitution, the optical axis of the first parabolic group reflecting surface generally and preferably corresponds to the irradiation direction of the headlight.
In the vehicle headlight with the constitution above, it is preferable to set the optical axis of the first parabolic group reflecting surface such that the reflected light from the first parabolic group reflecting surface outwardly irradiates on a side of the irradiated area of the reflected light from the first ellipse group reflecting surface.